A nanowaveguide platform for collective atom-light interaction

TL;DR

This paper introduces a silicon nitride nanowaveguide platform capable of trapping and probing rubidium atoms via evanescent fields, enabling efficient atom-light interactions for quantum applications.

Contribution

The authors develop a nanowaveguide with high coupling efficiency and thermal conductance, demonstrating atom trapping and initial atom-light interaction experiments.

Findings

Achieved ~80% fiber-to-waveguide coupling efficiency.

Observed thermal atom absorption in the evanescent field.

Demonstrated a U-wire magneto-optical trap near the waveguide surface.

Abstract

We propose a nanowaveguide platform for collective atom-light interaction through evanescent field coupling. We have developed a 1cm-long silicon nitride nanowaveguide can use evanescent fields to trap and probe an ensemble of 87Rb atoms. The waveguide has a sub-micrometer square mode area and was designed with tapers for high fiber-to-waveguide coupling efficiencies at near-infrared wavelengths (750nm to 1100nm). Inverse tapers in the platform adiabatically transfer a weakly guided mode of fiber-coupled light into a strongly guided mode with an evanescent field to trap atoms and then back to a weakly guided mode at the other end of the waveguide. The coupling loss is -1dB per facet (~80% coupling efficiency) at 760nm and 1064nm, which is estimated by a propagation loss measurement with waveguides of different lengths. The proposed platform has good thermal conductance and can guide high optical powers for trapping atoms in ultra-high vacuum. As an intermediate step, we have observed thermal atom absorption of the evanescent component of a nanowaveguide, and have demonstrated the U-wire mirror magneto-optical trap that can transfer atoms to the proximity of the surface.